Polycarbonates suitable for use in optical articles

ABSTRACT

The invention relates to polycarbonates suitable for use in optical articles; the polycarbonates contain residues of alicyclic bisphenols and have properties particularly suited for use in high density optical data storage media. The polycarbonates further contain residues of other monomers, such as SBI and its derivatives; bisphenols, such as bisphenol A; CD-1 and its derivatives or some combination of each.

FIELD OF THE INVENTION

This invention relates to polycarbonates suitable for use in opticalarticles, and methods for making such polycarbonates. This inventionfurther relates to optical articles, and methods for making opticalarticles from the polycarbonates.

BACKGROUND OF THE INVENTION

Polycarbonates and other polymer materials are utilized in optical datastorage media, such as compact disks. In optical data storage media, itis critical that polycarbonate resins have good performancecharacteristics such as transparency, low water affinity, goodprocessibility, good heat resistance and low birefringence. Highbirefringence is particularly undesirable in high density optical datastorage media.

Improvements in optical data storage media, including increased datastorage density, are highly desirable, and achievement of suchimprovements is expected to improve well established and new computertechnology such as read only, write once, rewritable, digital versatileand magneto-optical (MO) disks.

In the case of CD-ROM technology, the information to be read isimprinted directly into a moldable, transparent plastic material, suchas bisphenol A (BPA) polycarbonate. The information is stored in theform of shallow pits embossed in a polymer surface. The surface iscoated with a reflective metallic film, and the digital information,represented by the position and length of the pits, is read opticallywith a focused low power (5 mW) laser beam. The user can only extractinformation (digital data) from the disk without changing or adding anydata. Thus, it is possible to "read" but not to "write" or "erase"information.

The operating principle in a WORM drive is to use a focused laser beam(20-40 mW) to make a permanent mark on a thin film on a disk. Theinformation is then read out as a change in the optical properties ofthe disk, e.g., reflectivity or absorbance. These changes can takevarious forms: "hole burning" is the removal of material, typically athin film of tellurium, by evaporation, melting or spalling (sometimesreferred to as laser ablation); bubble or pit formation involvesdeformation of the surface, usually of a polymer overcoat of a metalreflector.

Although the CD-ROM and WORM formats have been successfully developedand are well suited for particular applications, the computer industryis focusing on erasable media for optical storage (EODs). There are twotypes of EODs: phase change (PC) and magneto-optic (MO). In MO storage,a bit of information is stored as a ˜1 μm diameter magnetic domain,which has its magnetization either up or down. The information can beread by monitoring the rotation of the plane polarization of lightreflected from the surface of the magnetic film. This rotation, calledthe Magneto-Optic Kerr Effect (MOKE) is typically less than 0.5 degrees.The materials for MO storage are generally amorphous alloys of the rareearth and transition metals.

Amorphous materials have a distinct advantage in MO storage as they donot suffer from "grain noise", spurious variations in the plane ofpolarization of reflected light caused by randomness in the orientationof grains in a polycrystalline film. Bits are written by heating abovethe Curie point, T_(c), and cooling in the presence of a magnetic field,a process known as thermomagnetic writing. In the phasechange material,information is stored in regions that are different phases, typicallyamorphous and crystalline. These films are usually alloys or compoundsof tellurium which can be quenched into the amorphous state by meltingand rapidly cooling. The film is initially crystallized by heating itabove the crystallization temperature. In most of these materials, thecrystallization temperature is close to the glass transitiontemperature. When the film is heated with a short, high power focusedlaser pulse, the film can be melted and quenched to the amorphous state.The amorphized spot can represent a digital "1" or a bit of information.The information is read by scanning it with the same laser, set at alower power, and monitoring the reflectivity.

In the case of WORM and EOD technology, the recording layer is separatedfrom the environment by a transparent, non-interfering shielding layer.Materials selected for such "read through" optical data storageapplications must have outstanding physical properties, such asmoldability, ductility, a level of robustness compatible with popularuse, resistance to deformation when exposed to high heat or highhumidity, either alone or in combination. The materials should alsointerfere minimally with the passage of laser light through the mediumwhen information is being retrieved from or added to the storage device.

As data storage densities are increased in optical data storage media toaccommodate newer technologies, such as digital versatile disks (DVD)and higher density data disks for short or long term data archives, thedesign requirements for the transparent plastic component of the opticaldata storage devices have become increasingly stringent. In many ofthese applications, previously employed polycarbonate materials, such asBPA polycarbonate materials, are inadequate. Materials displaying lowerbirefringence at current, and in the future progressively shorter"reading and writing" wavelengths have been the object of intenseefforts in the field of optical data storage devices.

Low birefringence alone will not satisfy all of the design requirementsfor the use of a material in optical data storage media; hightransparency, heat resistance, low water absorption, ductility, highpurity and few inhomogeneities or particulates are also required.Currently employed materials are found to be lacking in one or more ofthese characteristics, and new materials are required in order toachieve higher data storage densities in optical data storage media. Inaddition, new materials possessing improved optical properties areanticipated to be of general utility in the production of other opticalarticles, such as lenses, gratings, beam splitters and the like.

Birefringence in an article molded from polymeric material is related toorientation and deformation of its constituent polymer chains.Birefringence has several sources, including the structure and physicalproperties of the polymer material, the degree of molecular orientationin the polymer material and thermal stresses in the processed polymermaterial. For example, the birefringence of a molded optical article isdetermined, in part, by the molecular structure of its constituentpolymer and the processing conditions, such as the forces applied duringmold filling and cooling, used in its fabrication which can createthermal stresses and orientation of the polymer chains.

The observed birefringence of a disk is therefore determined by themolecular structure, which determines the intrinsic birefringence, andthe processing conditions, which can create thermal stresses andorientation of the polymer chains. Specifically, the observedbirefringence is typically a function of the intrinsic birefringence andthe birefringence introduced upon molding articles, such as opticaldisks. The observed birefringence of an optical disk is typicallyquantified using a measurement termed "vertical birefringence" or VBR,which is described more fully below.

Two useful gauges of the suitability of a material for use as a moldedoptical article, such as a molded optical data storage disk, are thematerial's stress optical coefficient in the melt (C_(m)) and its stressoptical coefficient in the glassy state (C_(g)), respectively. Therelationship between C_(m), C_(g) and birefringence may be expresses asfollows:

    Δn=C.sub.m ×Δσ.sub.m               (1)

    Δn=C.sub.g ×Δσ.sub.g               (2)

where Δn is the measured birefringence and Δσ_(m) and Δσ_(g) are theapplied stresses in the melt and glassy states, respectively. The stressoptical coefficients C_(m) and C_(g) are a measure of the susceptibilityof a material to birefringence induced as a result of orientation anddeformation occurring during mold filling and stresses generated as themolded article cools.

The stress optical coefficients C_(m) and C_(g) are useful as generalmaterial screening tools and may also be used to predict the verticalbirefringence (VBR) of a molded article, a quantity critical to thesuccessful use of a given material in a molded optical article. For amolded optical disk, the VBR is defined as:

    VBR=(v.sub.r -n.sub.z)=Δn.sub.rz                     (3)

where n_(r) and n_(z) are the refractive indices along the r an zcylindrical axes of the disk; n_(r) is the index of refraction seen by alight beam polarized along the radial direction, and n_(z) is the indexof refraction for light polarized perpendicular to the plane of thedisk. The VBR governs the defocusing margin, and reduction of VBR willlead to alleviation of problems which are not correctable mechanically.

In the search for improved materials for use in optical articles, Cm andCg are especially useful since they require minimal amounts of materialand are relatively insensitive to uncontrolled measurement parameters orsample preparation methods, whereas measurement of VBR requiressignificantly larger amounts of material and is dependent upon themolding conditions. In general, it has been found that materialspossessing low values of C_(g) and C_(m) show enhanced performancecharacteristics, for example VBR, in optical data storage applicationsrelative to materials having higher values of C_(g) and C_(m).Therefore, in efforts aimed at developing improved optical quality,widespread use of C_(g) and C_(m) measurements is made in order to rankpotential candidates for such applications and to compare them withpreviously discovered materials.

In applications requiring higher storage density, the properties of lowbirefringence and low water absorption in the polymer material fromwhich the optical article is fabricated become even more critical. Inorder to achieve higher data storage density, low birefringence isnecessary so as to minimally interfere with the laser beam as it passesthrough the optical article, for example a compact disk.

Another critical property needed for high data storage densityapplications is disk flatness. It is known that excessive moistureabsorption results in disk skewing which in turn leads to reducedreliability. Since the bulk of the disk is comprised of the polymermaterial, the flatness of the disk depends on the low water absorptionof the polymeric material. In order to produce high quality disksthrough injection molding, the polymer, such as polycarbonate should beeasily processed.

U.S. Pat. No. 4,950,731 discloses polycarbonate materials or use inoptical materials derived from bisphenol A and SBI. Bisphenol Apolycarbonate has high stress optical coefficient in the melt phase(C_(m)) and a high stress optical coefficient in the glassy state(C_(g)) which is moderated by the incorporation of6,6'-dihydroxy-3,3,3',3'-tetramethylspirobiindane (SBI), thehomopolycarbonate of which has a negative C_(m) value. Copolycarbonatesprepared from BPA and SBI have been shown to possess stress opticalcoefficients in the melt (C_(m)) of zero or near zero. Such copolymerslack the processibility of bisphenol A polycarbonate, however, and havehigher affinity for water.

U.S. Pat. No. 5,132,154 discloses polycarbonate mixtures in opticalapplications. The polycarbonate resin comprises units which contain abisphenol having an alicyclic ring structure, which is substituted byalkyl groups on at least one member of the ring structure. Such polymersare not the subject of this invention.

Japanese Kokai Patent Application No. 3-237130 discloses a polyetherresin for use in optical materials. The disclosure relates to polyetherresin and not polycarbonate resin, see page 4, last line.

Japanese Kokai Patent Application No. 4-41524 discloses a polyestercarbonate for use in optical materials. The polyester carbonate resincomprises units derived from phthalic acid. Such polymers are not thesubject of this invention.

Japanese Kokai Patent Application No. 3-221523 discloses a polyformalresin for use in optical articles obtained by the reaction of a divalentphenolic compound and a dihalogen compound. The reference does notrelate to polycarbonate resins as disclosed on page 4, and characterizespolycarbonate resin as exhibiting high birefringence, as disclosed onpage 4, lines 8-11.

Japanese Kokai Patent Application No. 3-162413 discloses a polymer foruse in optical materials. The polymer comprises residues ofspirobichroman. Such polymers are not the subject of this invention.

Japanese Kokai Patent Application No. 10-176046 discloses apolycarbonate copolymer for use in optical articles comprising residuesof 2-2-bis(3-tert-butyl-4-hydroxy-6-methylphenyl)-n-butane. Suchpolymers are not the subject of this invention.

Japanese Kokai Patent Application No. 4-345616 discloses a polycarbonatewhich may be used in optical recording media, the polycarbonatecomprising BPA or other aromatic hydroxy compounds and SBI.

Japanese Kokai Patent Application No. 9-6023 discloses a copolymerbinder with abrasion resistance and cracking resistance for use inphotoresists. There is no disclosure of optical materials havingbirefringence and other properties suitable for use in optical articles,or optical articles made from these materials.

Examined Japanese Patent No. 06-52585 discloses a copolymer which may beused in optical materials. The starting materials may include bisphenolssuch as 1,1-bis (4'-hydroxyphenyl)cyclohexane.

U.S. Pat. No. 5,858,833 and EP 0846711 disclose optical disk gradecopolyestercarbonates derived from hydroxyphenylindanols, having unitsderived from 6-hydroxy-1-(4'-hydroxyphenyl)-1,3,3-trimethylindane(CD-1).

U.S. Pat. No. 4,304,899 and EP 0016167 disclose polycarbonatecompositions having improved barrier properties. The disclosures do notteach compositions for use in optical media.

U.S. Pat. No. 5,424,389 discloses copolymers of bisphenol A and SBI foruse in optical applications. Such copolymers are not the subject of thisinvention.

U.S. Pat. No. 5,633,060 discloses an optical disk substrate derived from1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (BPI). Additionallythe polycarbonate may comprise units derived from4,4'-(m-phenylenediisopropylidene)diphenol and/or2,2-bis(3-methyl-4-hydroxyphenyl)propane. Polycarbonates based on BPIare not the subject of this invention.

There exists a need for compositions having good optical properties andgood processibility and which are suitable for use in high densityoptical recording media. Polycarbonates manufactured by copolymerizingthe aforementioned aromatic dihydroxy compounds, such as bisphenol A,with other monomers, such as SBI, may produce acceptable birefringence;however the glass transition temperature is often too high, resulting inpoor processing characteristics. Consequently, the obtained moldingshave low impact resistance. Further, the water absorption of suchpolycarbonates is unacceptable for higher density applications.

SUMMARY OF THE INVENTION

The present invention solves these problems, and provides furthersurprising properties. These and further objects of the invention willbe more readily appreciated when considering the following disclosureand appended claims.

In one aspect, the invention relates to polycarbonates comprising:

(a) carbonate structural units corresponding to structure (I) ##STR1##where R₁ and R₂ are independently selected from the group consisting ofC₁ -C₆ alkyl;

X represents CH₂ ;

m is an integer from 4 to 7;

n is an integer from 1 to 4; and

p is an integer from 1 to 4

with the proviso that at least one of R₁ or R₂ is in the 3 or 3'position;

(b) carbonate structural units selected from the group consisting of

(1) carbonate structural units corresponding to ##STR2## where R₃, R₄and R₆ independently represent C₁ -C₆ alkyl,

each R₅ is independently selected from the group consisting of H and C₁-C₃ alkyl and each n independently selected from the group consisting of0,1 and 2,

R₇ is H or C₁ -C₅ alkyl,

(2) carbonate structural units corresponding to ##STR3## where R₈, R₉,R₁₂ and R₁₃ are independently C₁ -C₆ alkyl,

R₁₀ and R₁₁ are independently H or C₁ -C₅ alkyl,

each R₁₄ is independently selected from the group consisting of H and C₁-C₃ alkyl and each n is independently selected from the group consistingof 0, 1 and 2;

(3) carbonate structural units corresponding to ##STR4## where R₁₅ isselected independently from the group consisting of H and C₁ -C₃ alkyl,and R₁₆ and R₁₇ are independently C₁ -C₆ alkyl or aryl;

(4) carbonate structural units corresponding to a mixture of structures(II) and (III); and

(5) carbonate structural units corresponding to a mixture of structures(III) and (IV),

where the polycarbonate has a glass transition temperature of from about120° C. to about 185° C. and a water absorption of below about 0.33%.

This invention further relates to method of making these polycarbonates,optical articles made from these polycarbonates, and methods of makingoptical articles from these polycarbonates.

In another aspect, the invention relates to optical articles comprising:

(1) from 90 to 100% by weight of a polycarbonate comprising structuralunits of the formula (I) ##STR5## where R₁ and R₂ are independentlyselected from the group consisting of C₁ -C₆ alkyl;

X represents CH₂ ;

m is an integer from 4 to 7;

n is an integer from 1 to 4; and

p is an integer from 1 to 4

with the proviso that at least one of R₁ or R₂ is in the 3 or 3'position; and wherein the structural units of formula (I) comprise from90 to 100 mol % of the polycarbonate; and

(2) from 0 to 10% by weight of further additives;

where the polycarbonate has a glass transition temperature of from about120° C. to about 185° C. and a water absorption of below about 0.33%.

The invention further relates to methods of making optical articles fromthese compositions. In one embodiment of this invention, structure (I)is 1,1-bis(4-hydroxy-3-methyl phenyl) cyclohexane (BCC), and in anotherembodiment, the polycarbonate is a homopolycarbonate of BCC.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of preferred embodiments of the inventionand the Examples included therein.

Before the present compositions of matter and methods are disclosed, itis to be understood that this invention is not limited to specificsynthetic methods or to particular formulations, as such may, of course,vary. It is also to be understood that the terminology used herein isfor the purpose of describing particular embodiments only and is notintended to be limiting.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings.

The singular forms "a," "an" and "the" include plural referents unlessthe context clearly dictates otherwise.

"Optional" or "optionally" means that the subsequently described eventor circumstances may or may not occur, and that description includesinstances where the event or circumstance occurs and instances where itdoes not.

"BPA" is herein defined as bisphenol A or2,2-bis(4-hydroxyphenyl)propane.

"SBI" is herein defined as6,6'-dihydroxy-3,3,3',3'-tetramethylspirobiindane.

"BCC" is herein defined as 1,1-bis(4-hydroxy-3-methyl phenyl)cyclohexane.

"CD-1" is herein defined as6-hydroxy-1-(4'-hydroxyphenyl)-1,3,3-trimethylindane.

"C_(g) " is the stress optical coefficient of a polymeric material inthe glassy state, measured in Brewsters (10⁻¹³ cm² /dyne)

"C_(m) " is the stress optical coefficient in the melt phase, measuredin Brewsters (10⁻¹³ cm² /dyne)

"Polycarbonate" or "polycarbonates" as used herein includescopolycarbonates, homopolycarbonates and (co)polyester carbonates.

"Optical articles" as used herein includes optical disks and opticaldata storage media, for example a compact disk (CD audio or CD-ROM), adigital versatile disk, also known as DVD (ROM, RAM, rewritable), amagneto optical (MO) disk and the like; optical lenses, such as contactlenses, lenses for glasses, lenses for telescopes, and prisms; opticalfibers; information recording media; information transferring media;high density data storage media, disks for video cameras, disks forstill cameras and the like; as well as the substrate onto which opticalrecording material is applied. In addition to use as a material toprepare optical articles, the polycarbonate may be used as a rawmaterial for films or sheets.

Unless otherwise stated, "mol %" in reference to the composition of apolycarbonate in this specification is based upon 100 mol % of therepeating units of the polycarbonate. For instance, "a polycarbonatecomprising 90 mol % of BCC" refers to a polycarbonate in which 90 mol %of the repeating units are residues derived from BCC diphenol or itscorresponding derivative(s). Corresponding derivatives include but arenot limited to, corresponding oligomers of the diphenols; correspondingesters of the diphenol and their oligomers; and the correspondingchloroformates of the diphenol and their oligomers.

The terms "residues" and "structural units", used in reference to theconstituents of the polycarbonate, are synonymous throughout thespecification.

Throughout this application where publications are referenced, thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the state of the art to which this invention pertains.

I Polycarbonate Suitable for Use in Optical Articles

As mentioned, in one aspect, this invention relates to polycarbonatesand methods for preparing polycarbonates, the polycarbonate comprising:

(a) carbonate structural units corresponding to structure (I) ##STR6##where R₁ and R₂ are independently selected from the group consisting ofC₁ -C₆ alkyl;

X represents CH₂ ;

m is an integer from 4 to 7;

n is an integer from 1 to 4; and

p is an integer from 1 to 4

with the proviso that at least one of R₁ or R₂ is in the 3 or 3'position;

(b) carbonate structural units selected from the group consisting of

(1) carbonate structural units corresponding to ##STR7## where R₃, R₄and R₆ independently represent C ₁ -C₆ alkyl,

each R₅ is independently selected from the group consisting of H and C₁-C₃ alkyl and each n independently selected from the group consisting of0,1 and 2,

R₇ is H or C₁ -C₅ alkyl,

(2) carbonate structural units corresponding to ##STR8## where R₈, R₉,R₁₂ and R₁₃ are independently C₁ -C₆ alkyl,

R₁₀ and R₁₁ are independently H or C₁ -C₅ alkyl,

each R₁₄ is independently selected from the group consisting of H and C₁-C₃ alkyl and each n is independently selected from the group consistingof 0, 1 and 2;

(3) carbonate structural units corresponding to ##STR9## where R₁₅ isselected independently from the group consisting of H and C₁ -C₃ alkyl,and R₁₆ and R₁₇ are independently C₁ -C₆ alkyl or aryl;

(4) carbonate structural units corresponding to structures (II) and(III); and

(5) carbonate structural units corresponding to structures (III) and(IV),

where the polycarbonate has a glass transition temperature of from about120° C. to about 185° C. and a water absorption of below about 0.33%.

The present invention has solved the aforementioned proble ms ofprocessibility and water absorption, and provides a composition havinggood processibility and low water absorption. The composition furtherprovides polycarbonates having good optical properties and suitableglass transition temperatures, and which are suitable for use in opticalarticles. Suitable glass transition temperatures are necessary toprovide adequate processibility, for example good moldingcharacteristics.

Further, the applicants have found that polycarbonates comprising thedisclosed carbonate structural units are suitable for use in high datastorage density optical media. In particular the polycarbonates of thepresent invention have good transparency, low water absorption, asuitable stress optical coefficient, good processibility, and goodthermal stability.

Applicants have also unexpectedly found that polycarbonates comprisingunits of the structure: ##STR10## where R₁ and R₂ are independentlyselected from the group consisting of C₁ -C₆ alkyl;

X represents CH₂ ;

m is an integer from 4 to 7;

n is an integer from 1 to 4; and

p is an integer from 1 to 4

with the proviso that at least one of R₁ or R₂ is in the 3 or 3'position,

exhibit lower affinity for water and have unexpectedly low C_(g) values,in particular C_(g) values below about 60 Brewsters. It is critical thatthe structural units of formula I be substituted in the 3 or 3' positionby at least one of R₁ or R₂. It is preferable that n and p are equal toone, and that R₁ and R₂ are present in the 3 and 3' positions,respectively, as follows: ##STR11## R₁ and R₂ are preferably C₁ -C₆alkyl, more preferably C₁ -C₃ alkyl, even more preferably CH₃. Thepolycarbonate should comprise at least about 30 mol % of units ofstructure I to achieve an acceptable degree of low water absorption foruse in optical applications. These polycarbonates were further found tohave acceptable C_(m) values, i.e. below about 3,000 Brewsters.

In the present invention it is further critical that the polycarbonatesposses other suitable properties for use in optical media. Thepolycarbonates of this invention preferably have glass transitiontemperatures in the range of 120° to 185° C., more preferably 125° to165° C., even more preferably 130 to 150° C. The water absorption of thepolycarbonates is preferably below 0.33%, even more preferably less thanabout 0.2%.

The number average molecular weight (M_(w)) of the polycarbonate, asdetermined by gel permeation chromatography relative to polystyrene, ispreferably from about 10,000 to about 100,000, more preferably betweenabout 10,000 to about 50,000, even more preferably between about 12,000to about 40,000.

The polycarbonate should have light transmittance of at least about 85%,more preferably at least about 90% and a C_(g) of less than about 60Brewsters, more preferably less than 55 Brewsters, even more preferablyless than 50 Brewsters. The polycarbonate preferably has a C_(m) ofbelow about 3,000 Brewsters, more preferably below about 2,500Brewsters, even more preferably less than about 2,450 Brewsters.

The compositions of a particular polycarbonate may be varied withincertain ranges to achieve the suitable property profile. The followingdiscussion sets forth illustrative ranges for the desired embodiments.

In the embodiment where structure (II) is selected as component b),component a) preferably comprises from 30 to 99 mol %, even morepreferably 60 to 99 mol % of the polycarbonate. Carbonate units ofstructure (II) preferably comprise from 1 to 70 mol %, more preferablyfrom 1 to 40 mol % of the polycarbonate. Optionally the polycarbonatemay comprise from 0.1 to 20 mol % of structural units of structure (V):##STR12## wherein Z is a C₁ -C₄₀ branched or unbranched alkyl orbranched or unbranched cycloalkyl.

Representative units of component a) include, but are not limited toresidues of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (BCC);1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof.Residues of BCC are most preferred as component a). Representative unitsof component b) include, but are not limited to residues of6-hydroxy-1-(4'-hydroxyphenyl)-1,3,3-trimethylindane (CD-1);6-hydroxy-1-(4'-hydroxy-3'-methylphenyl)-1,3,3,5-tetramethylindane.Residues of CD-1 are most preferred as component b).

Representative units of structure (V) include, but are not limited, toresidues of dodecanedioic acid, sebacic acid, adipic acid,octadecanedioic acid, octadec-9 enedioic acid, 9-carboyxoctadecanoicacid and 10-carboxyoctadecanoic acid. Residues of dodecanedioic acid(DDDA) are the more preferred.

In the embodiment where structure (III) is selected as component b),component a) preferably comprises from about 30 to 99 mol % of thepolycarbonate, even more preferably from about 60 to 99 mol % of thepolycarbonate. Carbonate units of structure (III) preferably comprisefrom about 1 to about 70 mol % of the polycarbonate, even morepreferably form about 1 to about 40 mol % of the polycarbonate.Optionally, the polycarbonate may comprise from 0.1 to 20 mol % ofcarbonate units of structure (V), as defined.

Representative units of component a) include, but are not limited toresidues of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (BCC);1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof.Residues of BCC are most preferred as component a). Representative unitsof component b) include, but are not limited to residues of6,6'-dihydroxy-3,3,3',3'-tetramethyl spirobiindane(SBI);6,6'-dihydroxy-3,3,5,3',3',5'-hexamethyl spirobiindane;6,6'-dihydroxy-3,3,5,7,3',3',5',7'-octamethylspirobiindane;5,5'-diethyl-6,6'-dihydroxy 3,3,3',3'-tetramethylspirobiindane andmixtures thereof. Residues of SBI and its ortho alkylated homologs aremost preferred as component b).

Representative units of structure (V) include, but are not limited to,residues of dodecanedioic acid, sebacic acid, adipic acid,octadecanedioic acid, octadec-9-enedioic acid, 9-carboxyoctadecanoicacid and 10-carboxyoctadecanoic acid. Residues of dodecanedioic acid arethe more preferred.

In the embodiment where structure (IV) is selected as component b),component a) preferably comprises from 30 to 99 mol % of thepolycarbonate, more preferably from 60 to 99 mol % of the polycarbonate.Carbonate units of structure (IV) preferably comprise from 1.0 to 70 mol% of the polycarbonate, even more preferably from 1.0 to 40 mol % of thepolycarbonate, except in the case where component b) is selected to beresidues of BPA exclusively, i.e. 100 mol %, based on 100 mol % ofrepeating units b) in the polycarbonate.

In this case, the structural units corresponding to BPA comprise from0.1 to 50 mol % of the polycarbonate; it is further preferable in thiscase that component a) comprise at least 50 mol % of the polycarbonate;more preferably component a) is selected to be residues of BCC in thiscase.

In the case where structure (IV) is selected as component b), componentb) is selected to be exclusively BPA (i.e. 100 mol %, based on 100 mol %of repeating units of b) in the polycarbonate) and the optical articleto be formed from the polycarbonate is optical data storage media or asubstrate for optical data storage media requiring C_(m) of 3000 or lessand C_(g) of 50 Brewsters or less, it is particularly preferred that thepolycarbonate comprise no more than 20 mol % of residues of BPA. In thiscase, the polycarbonate preferably comprises from 80 to 85 mol % BCC andfrom 15 to 20 mol % BPA. In one embodiment the polycarbonate is 80 mol %of residues of BCC and 20 mol % of residues of BPA.

In the embodiment where structure (IV) is selected as component b), thepolycarbonate may optionally comprise from 0.1 to 20 mol % of carbonatestructural units of structure (V) as defined above.

Representative units of component a) include, but are not limited toresidues of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (BCC);1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof.Residues of BCC are preferred as component a). Representative units ofcomponent b) in the embodiment where structure (IV) is selected ascomponent b) include, but are not limited to residues of2,2-bis(4-hydroxyphenyl)propane (BPA); 2,2-bis(4-hydroxyphenyl)butane;2,2-bis(4-hydroxyphenyl)pentane;2,2-bis(4-hydroxy-3-methylphenyl)propane;2,2-bis(3-ethyl-4-hydroxyphenyl)propane; and mixtures thereof. Residuesof BPA are preferred as component b) in this embodiment.

Representative units of structure (V) include, but are not limited to,residues of dodecanedioic acid, sebacic acid, adipic acid,octadecanedioic acid, octadec-9-enedioic acid, 9-carboxyoctadecanoicacid and 10-carboxyoctadecanoic acid. Residues of dodecanedioic acid arethe more preferred.

In the embodiment where mixtures of structures (II) and (III) areselected as component b), component a) preferably comprises from 30 to99 mol % of the polycarbonate, even more preferably 60 to 99 mol % ofthe polycarbonate. Carbonate structural units of formulas (II) and (III)preferably comprise from 1 to 70 mol % of the polycarbonate, even morepreferably 1 to 40 mol % of the polycarbonate. The ratio of structuralunits (II) to (III) is preferably in the range of 1:99 to 99:1.Optionally, the polycarbonate in this embodiment may comprise from 0.1to 20 mol % of structure (V) as defined above.

Representative units of component a), include, but are not limited toresidues of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (BCC);1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof. BCCis most preferred as component a). Representative units of component b)in this embodiment include, but are not limited to6-hydroxy-1-(4'-hydroxyphenyl)-1,3,3-trimethylindane (CD-1);6-hydroxy-1-(4'-hydroxy-3'-methylphenyl)-1,3,3,5-tetramethylindane; and6,6'-dihydroxy-3,3,3',3'-tetramethyl spirobiindane(SBI);6,6'-dihydroxy-3,3,5,3',3',5'-hexamethyl spirobiindane;6,6'-dihydroxy-3,3,5,7,3',3',5',7'-octamethylspirobiindane;5,5'-diethyl-6,6'-dihydroxy-3,3,3',3'-tetramethylspirobiindane. Residuesof CD-1 and SBI are most preferred as structures (II) and (III),respectively.

Representative units of structure (V) in this embodiment include, butare not limited to residues of dodecanedioic acid, sebacic acid, adipicacid, octadecanedioic acid, octadec-9-enedioic acid,9-carboxyoctadecanoic acid and 10-carboxyoctadecanoic acid. Residues ofdodecanedioic acid are the more preferred acid.

In the embodiment where structures (III) and (IV) are selected ascomponent b), component a) preferably comprises from 30 to 99 mol % ofthe polycarbonate, even more preferably from 60 to 99 mol % of thepolycarbonate. Carbonate structural units of formulas (III) and (IV)preferably comprise from 1 to 70 mol % of the polycarbonate, even morepreferably from 1 to 40 mol % of the polycarbonate. The ratio ofstructural units (III) to (IV) is preferably in the range of 1:99 to99:1. Optionally, the polycarbonate in this embodiment may comprise fromabout 0.1 to 20 mol % of structure (V) as defined above.

Representative units of component a) include, but are not limited toresidues of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (BCC);1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof.Residues of BCC are most preferred as component a). Representative unitsof component b) in the embodiment where structures (III) and (IV) areselected as component b), include, but are not limited to, residues of6,6'-dihydroxy-3,3,3',3'-tetramethyl spirobiindane(SBI);6,6'-dihydroxy-3,3,5,3',3',5'-hexamethyl spirobiindane;6,6'-dihydroxy-3,3,5,7,3',3',5',7'-octamethylspirobiindane;5,5'-diethyl-6,6'-dihydroxy-3,3,3',3'-tetramethylspirobiindane; andresidues of 2,2-bis(4-hydroxyphenyl)propane (BPA);2,2-bis(4-hydroxyphenyl)butane; 2,2-bis(4-hydroxyphenyl)pentane;2,2-bis(4-hydroxy-3-methylphenyl)propane;2,2-bis(3-ethyl-4-hydroxyphenyl)propane; and mixtures thereof. Residuesof SBI and BPA are most preferred as structures (III) and (IV),respectively.

Representative units of structure (V) in this embodiment include, butare not limited to residues of dodecanedioic acid, sebacic acid, adipicacid, octadecanedioic acid, octadec-9-enedioc acid,9-carboxyoctadecanoic acid and 10-carboxyoctadecanoic acid. Residues ofdodecanedioic acid are the more preferred.

The polycarbonates of the invention may be prepared by the interfacialor the melt process. If the interfacial process is used, the addition ofvarious phase transfer catalysts is optional. Phase transfer catalystswhich are suitable include, but are not limited to tertiary amines, suchas triethylamine, ammonium salts, such as tetrabutylammonium bromide; orhexaethylguanidium chloride. Monofunctional phenols, such asp-cumylphenol and 4-butylphenol; long chain alkylphenols, such ascardanol and nonyl phenol; and difunctional phenols may be used as chainstopping agents. Optionally 0.1 to 10 mole %, more preferably 1 to 5mole % of chainstopping agent may be incorporated into thepolycarbonate, based on the total moles of the repeating units.

In some instances, the phosgenation conditions must be adjusted. Inparticular, the phosgenation conditions should be adjusted in caseswhere the formation of undesired cyclic oligomers is favored by thecharacteristic reactivity of the monomer, which is related to monomersolubility in the reaction medium and monomer structure. In the case ofBCC, for example, cyclic oligomer formation occurs to a greater extentunder standard interfacial polymerization conditions than in the caseof, for example, BPA. In polycarbonates containing substantial more thanabout 20 mol % of BCC, it is advantageous to use an excess of phosgeneto promote the formation of linear bischloroformate oligomers which areconverted to high molecular weight polymers by partial hydrolysis andpolycondensation. Preferably from about 20 to 200 mol % of excessphosgene is used.

The polycarbonates of the invention may also be prepared by the melt ortransesterification process. This process does not require the use ofphosgene or a solvent and minimizes the formation of low molecularweight contaminants, such as cyclic and linear low molecular weightoligomers in the final polymer. The monomers are mixed with a carbonatesource, such as a diarylcarbonate, and a small amount of catalyst, suchas an alkali metal hydroxide or ammonium hydroxide and heated under avacuum according to a protocol in which the temperature is raisedthrough a series of stages while the pressure in the headspace over thereaction mixture is lowered from ambient pressure to about 1 torr.

Suitable carbonate sources, catalysts and reaction conditions are foundin U.S. Pat. No. 5,880,248, and Kirk-Othmer Encyclopedia of ChemicalTechnology, Fourth Edition, Volume 19, pp. 585-600, herein incorporatedby reference. The time of the stages and the temperature are such thatmechanical losses of material through foaming and the like are avoided.Phenol and excess diphenyl carbonate are removed overhead to completethe polymerization process. The product high polymer is then isolated asa melt which may be compounded with other additives, such as stabilizersand mold release agents prior to pelletization. The products produced bythe melt process have reduced numbers of undissolved particles andreduced content of low molecular weight contaminants, such as cyclicoligomers, relative to the interfacially produced product.

It was unexpectedly found that for a preferred embodiment of theinvention, where the polycarbonate comprises 84 mol % BCC and 16 mol %SBI, the melt process produced a superior product. In particular, themelt process produced a polycarbonate having a C_(g) of 38 Brewsters.For the same composition produced by the interfacial process, thepolycarbonate was found to have a C_(g) of 45.1 Brewsters.

In this embodiment, the polycarbonate preferably has a T_(g) below about150° C., a water absorption below about 0.2% a C_(g) below about 50Brewsters and a C_(m) of less than about 2500 Brewsters.

The method to prepare the polycarbonate comprising 84 mol % BCC and 16mol % SBI preferably comprises the steps of:

A) mixing BCC monomer and SBI monomer in a molar ratio of BCC:SBI of84:16 with a carbonate source in the presence of a catalyst, therebyforming a reaction mixture;

B) heating the reaction mixture until the reaction mixture melts;

C) thermally equilibrating the mixture; and

D) increasing the molecular weight by removing volatile components fromthe reaction mixture in one or more reaction stages.

The volatile components include phenol and excess diphenyl carbonate.The number average molecular weight (M_(w)) of the polycarbonatecomprising 84 mol % BCC and 16 mol % SBI, as determined by gelpermeation chromatography relative to polystyrene, is preferably fromabout 10,000 to about 100,000, more preferably between about 10,000 toabout 50,000, even more preferably between about 12,000 to about 40,000.

The polycarbonates of the present invention may optionally be blendedwith any conventional additives used in optical applications, includingbut not limited to dyestuffs, UV stabilizers, antioxidants, heatstabilizers, and mold release agents, to form an optical article. Inparticular, it is preferable to form a blend of the polycarbonate andadditives which aid in processing the blend to form the desired opticalarticle. The blend may optionally comprise from 0.0001 to 10% by weightof the desired additives, more preferably from 0.0001 to 1.0% by weightof the desired additives.

Substances or additives which may be added to the polycarbonates of thisinvention, include, but are not limited to, heat-resistant stabilizer,UV absorber, mold-release agent, antistatic agent, slip agent,antiblocking agent, lubricant, anticlouding agent, coloring agent,natural oil, synthetic oil, wax, organic filler, inorganic filler andmixtures thereof.

Examples of the aforementioned heat-resistant stabilizers, include, butare not limited to, phenol stabilizers, organic thioether stabilizers,organic phosphide stabilizers, hindered amine stabilizers, epoxystabilizers and mixtures thereof. The heat-resistant stabilizer may beadded in the form of a solid or liquid.

Examples of UV absorbers include, but are not limited to, salicylic acidUV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers,cyanoacrylate UV absorbers and mixtures thereof.

Examples of the mold-release agents include, but are not limited tonatural and synthetic paraffins, polyethylene waxes, fluorocarbons, andother hydrocarbon mold-release agents; stearic acid, hydroxystearicacid, and other higher fatty acids, hydroxyfatty acids, and other fattyacid mold-release agents; stearic acid amide, ethylenebisstearoamide,and other fatty acid amides, alkylenebisfatty acid amides, and otherfatty acid amide mold-release agents; stearyl alcohol, cetyl alcohol,and other aliphatic alcohols, polyhydric alcohols, polyglycols,polyglycerols and other alcoholic mold release agents; butyl stearate,pentaerythritol tetrastearate, and other lower alcohol esters of fattyacid, polyhydric alcohol esters of fatty acid, polyglycol esters offatty acid, and other fatty acid ester mold release agents; silicone oiland other silicone mold release agents, and mixtures of any of theaforementioned.

The coloring agent may be either pigments or dyes. Inorganic coloringagents and organic coloring agents may be used separately or incombination in the invention.

The polycarbonates may be random copolymers, block copolymers or graftcopolymers. When graft copolymers and other branched polymers areprepared a suitable branching agent is used during production.

The desired optical article may be obtained by molding the polycarbonateor polycarbonate blend by injection molding, compression molding,extrusion methods and solution casting methods. Injection molding is themore preferred method of forming the article.

Because the polycarbonates of the present invention possess advantageousproperties such as low water absorption, good processibility and lowbirefringence, they can be advantageously utilized to produce opticalarticles. End-use applications for the optical article of the inventioninclude, but are not limited to, a digital audio disk, a digitalversatile disk, an optical memory disk, a compact disk, an ASMO deviceand the like; optical lenses, such as contact lenses, lenses forglasses, lenses for telescopes, and prisms; optical fibers; magnetooptical disks; information recording media; information transferringmedia; disks for video cameras, disks for still cameras and the like.

The polycarbonate may function as the medium for data storage, i.e. thedata may be fixed onto or into the polycarbonate. The polycarbonate mayalso function as the substrate onto which a data storage medium isapplied. Further, some combination of both functions may be employed ina single device, as for instance when the polycarbonate is imprintedwith tracking to aid in reading a data storage medium which is appliedto the polycarbonate.

II. Optical Articles Containing at least 90 wt % of a PolycarbonateDerived from Alicyclic Bisphenols and Polycarbonates of AlicyclicBisphenols

In a further aspect, the invention relates to an optical articlecomprising:

(1) from 90 to 100% by weight of a polycarbonate having carbonatestructural units corresponding to structure (I): ##STR13## where R₁ andR₂ are independently selected from the group consisting of C₁ -C₆ alkyl;

X represents CH₂ ;

m is an integer from 4 to 7;

n is an integer from 1 to 4; and

p is an integer from 1 to 4

with the proviso that at least one of R₁ or R₂ is in the 3 or 3'position; and wherein the structural units of formula (I) comprise from90 to 100 mol % of the polycarbonate; and

(2) from 0 to 10% by weight of further additives;

where the polycarbonate has a glass transition temperature of from about120° C. to about 185° C. and a water absorption of below about 0.33%.

The invention further relates to the polycarbonates comprising theoptical article as defined above, the polycarbonates having carbonatestructural units corresponding to structure (I): ##STR14## where R₁ andR₂ are independently selected from the group consisting of C₁ -C₆ alkyl;

X represents CH₂ ;

m is an integer from 4 to 7;

n is an integer from 1 to 4; and

p is an integer from 1 to 4

with the proviso that at least one of R₁ or R₂ is in the 3 or 3'position; and wherein the structural units of formula (I) comprise from90 to 100 mol % of the polycarbonate; and where the polycarbonate has aglass transition temperature of from about 120° C. to about 185° C. anda water absorption of below about 0.33%.

In one embodiment of the invention, the polycarbonate is 100 mol % ofresidues BCC. In the embodiment where the polycarbonate is 100 mol % ofresidues of BCC, the polycarbonate has a glass transition temperature ofbelow about below about 150° C. and a water absorption of below about0.15%. The homopolycarbonate has a C_(g) of below about 50 Brewsters anda C_(m) of below about 2500 Brewsters.

Representative units of structure (I) in the polycarbonate, include, butare not limited to residues of1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane (BCC);1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof.Residues of BCC are most preferred as component a). The bisphenolscorresponding to structure (I) are herein referred to as "alicyclicbisphenols".

In one embodiment of the optical article as defined, component (1) ofthe optical article is a polycarbonate of 100 mol % of residues of BCC,structure (VI). BCC may be easily synthesized from cyclohexanone andortho-cresol. ##STR15## A polycarbonate, comprising 100 mol % ofstructural units derived from BCC, is herein referred to as "BCChomopolycarbonate".

It was unexpectedly found that polycarbonates comprising 90 to 100 mol %of structure (I) possess unexpectedly low values for C_(g), as well aslow water affinity, and suitable processibility, and are particularlysuited for use in optical articles. It is critical that the structuralunits of formula (I) be substituted in the 3 or 3' position by at leastone of R₁ or R₂. It is preferable that n and p are equal to one, andthat R₁ and R₂ are present in the 3 and 3' positions, respectively. R₁and R₂ are preferably C₁ -C₆ alkyl, more preferably C₁ -C₃ alkyl, evenmore preferably CH₃. It was further found that polycarbonates comprising90 to 100 mol % of units of structural formula (I) possess acceptableC_(m) values, i.e. values below about 3,000 Brewsters.

In the present invention it is further critical that the polycarbonatesposses suitable properties for use in optical articles. Thepolycarbonates of the further aspect of the invention preferably haveglass transition temperatures in the range of 120° to 185° C., morepreferably 125° to 165° C., even more preferably 130 to 150° C.

The water absorption of the polycarbonates is preferably below 0.33%,even more preferably less than about 0.2%.

The weight average molecular weight (M_(w)), as determined by gelpermeation chromotagraphy relative to polystyrene, of the polycarbonatesis preferably from about 10,000 to about 100,000, more preferablybetween about 10,000 to about 50,000, even more preferably between about20,000 to about 30,000.

The polycarbonates should have light transmittance of at least about85%, more preferably at least about 90% and a C_(g) of less than about60 Brewsters, more preferably less than 50 Brewsters. The polycarbonatespreferably have a C_(m) of below about 3,000 Brewsters, even morepreferably below about 2,500 Brewsters.

The desired optical article may be obtained by molding the polycarbonateor polycarbonate blend by injection molding, compression molding,extrusion methods and solution casting methods. Injection molding is themore preferred method of forming the article.

The methods of making the polycarbonates, end use applications, andadditives that may be blended with the polycarbonates are the same asthose described in section I of this specification, in reference to thepolycarbonate suitable for use in an optical article.

As mentioned in reference to the polycarbonates in section I of thisspecification, the polycarbonate of the further aspect of the inventionas defined in section II, and the optical articles made therefrom, mayfunction as the medium for data storage, as in CD audio, CD ROM and readonly DVD i.e. the data may be fixed onto or into the polycarbonate. Thepolycarbonate may also function as the substrate onto which a datastorage medium is applied. Further, some combination of both functionsmay be employed in a single device, as for instance when thepolycarbonate is imprinted with tracking to aid in reading a datastorage medium which is applied to the polycarbonate.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompositions of matter and methods claimed herein are made andevaluated, and not intended to limit the scope of what the inventorsregard as their invention. Efforts have been made to insure accuracywith respect to numbers (e.g., amounts, temperatures, etc.) but someerror and deviations should be accounted for. Unless indicatedotherwise, parts are by weight, temperature is in ° C. or is at roomtemperature and pressure is at or near atmospheric.

The materials and testing procedures used for the results shown hereinare as follows:

Molecular weights are reported as weight average (M_(w)) and weredetermined by gel permeation chromatography relative to polystyrene.

Water absorption (% H₂ O) was determined by ASTM procedure D-0570.

T_(g) values were determined by differential scanning calorimetry.

C_(g) values were determined as follows. The polycarbonate (7.0 grams)was charged to a heated mold having dimensions 5.0×0.5 inches andcompression molded at 120° C. above its glass transition temperaturewhile being subjected to applied pressure starting at 0 and ending at2000 pounds using a standard compression molding device. After therequired amount of time under these conditions the mold was allowed tocool and the molded test bar removed with the aid of a Carver press. Themolded test bar was then inspected under a polaroscope and anobservation area on the test bar located. Selection of the observationarea was based on lack of birefringence observed and sufficient distancefrom the ends or sides of the test bar. The sample was then mounted in adevice designed to apply a known amount of force vertically along thebar while the observation area of the bar was irradiated withappropriately polarized light. The bar was then subjected to six levelsof applied stress and the birefringence at each level measured with theaid of a Babinet compensator. Plotting birefringence versus stressaffords a line whose slope is equal to the stress optical coefficientC_(g).

Cm values are reported at T_(g) +100 degrees Celcius. A rectangularsample was subjected to a known oscillary strain rate and the shearstress was monitored. Simultaneously, a polarized laser beam was sentparallel to the shear plane. The birefringence and orientation weremeasured by modulating the light with a electrooptic modulator andmonitoring the in-phase and out of phase component of the wave at thedetector as taught by Kanana, M. R. and Kornfield, J. A, Journal ofRheology, 1994, 38(4).

Example 1

A 500 mL Morton flask equipped with a magnetic stirrer, refluxcondenser, dual nitrogen and phosgene inlet tube and exit tube attachedto a base scrubbing system was charged with BCC (21.4 g, 72.3 mmol), SBI(4.24 g, 13.8 mmol), p-cumylphenol (0.82 g, 3.9 mmol, 4.5 mol %),methylene chloride (110 mL) and distilled water (80 mL). The reactionmixture was treated with 50 wt % NaOH to bring the pH to 10.5. Phosgene(17.0 g, 170 mmol, 100 mol % excess) was added at 0.6 g/min maintainingthe pH at 10.5 by the addition of the NaOH solution. The chloroformatesolution was treated with triethylamine (0.20 mL, 2 mol %) and avigorous reflux ensued. The 15 pH was maintained at 10.5. Under theseconditions an analytical test for chloroformates indicated theircomplete absence after about 2 min. The resultant polymer solution wasseparated from the brine and washed once with 1N HCl and four times withdistilled water. The polymer solution was precipitated into boilingwater (750 mL) in a blender, washed with water (500 mL) and driedovernight at 125° C. under vacuum. The polymer had a Mw of 32,500 and aTg of 149° C.

Example 2

BCC (19.62 g, 67.7 mmol), CD-1 (5.31 g, 19.8 mmol), p-cumylphenol (0.82g, 3.9 mmol, 4.5 mol %) were reacted with phosgene as in Example 1 toafford after isolation a polycarbonate having a glass transitiontemperature of 148° C.

Example 3

A 500 mL Morton flask equipped as in example 1 was charged with BCC(26.9 g, 100 mmol), methylene chloride (125 mL) and distilled water (90mL). The reaction mixture was treated with 50 wt % NaOH to bring the pHto 10.5. Phosgene (20.3 g, 205 mmol, 105 mol % excess) was metered intothe reaction mixture at 0.6 g/min maintaining the pH at 10.5 by theaddition of the NaOH solution. After 10.0 grams of phosgene had beenadded p-cumylphenol (1.06 g, 5.0 mmol, 5 mol %) was added. When thephosgene addition was complete triethylamine (0.125 mL, 0.9 mmol) wasadded and sufficient 50% NaOH was added to maintain the a pH of 10.9.After 2 minutes no chloroformates were detectable in the reactionmixture. Additional triethylamine (0.125 mL, 0.9 mmol) was added andadditional phosgene (4.5 g, 45 mmol) was metered into the reactionmixture at 0.6 g/min. The polymer solution was separated from the brineand washed once with 1N HCl and four times with distilled water. Thepolymer solution was precipitated into boiling water (750 mL) in ablender, washed with water (500 mL) and dried overnight at 110° C. undervacuum. The polymer had a Tg of 138° C.

Example 4

BCC (24.0 g, 80 mmol), BPA (4.56 g, 20 mmol) and p-cumylphenol (1.06 g,5 mmol, 5 mol %) were reacted with phosgene as in Example 3 to affordafter isolation a polycarbonate having a glass transition temperature of138° C.

Example 5

BCC (17.8 g, 60 mmol), BPA (9.12 g, 40 mmol) and p-cumylphenol (1.06 g,5 mmol, 5 mol %) were reacted with phosgene as in Example 3 to affordafter isolation a polycarbonate having a glass transition temperature of139° C.

Example 6

A 500 mL Morton flask equipped as in example 1 was charged with BCC(22.2 g, 74.9 mmol), SBI (7.7 g, 25 mmol), dodecanedioic acid (DDDA,1.24 g, 5.4 mmol) methylene chloride (125 mL) and distilled water (100mL) and triethylamine (200 uL). The reaction mixture was treated with 50wt % NaOH to bring the pH to 8.5. Phosgene (6 g, 60 mmol) was meteredinto the reaction mixture at 0.6 g/min maintaining the pH at 8.5 by theaddition of the NaOH solution. At this point p-cumylphenol (0.95 g, 4.5mmol) was added and an additional 1 g of phosgene was metered into thereaction mixture at pH 8.5. Phosgenation was halted and the pH wasraised to 11 by addition of 50% NaOH. Phosgene addition was resumed atpH 11 until a total of 15.1 g (50 mole % excess) phosgene had beenadded. At this stage the mixture tested positive for chloroformategroups. Triethylamine (200 uL) and a trace of 4-dimethylaminopyridine(several crystals) were added after which the mixture showed the absenceof chloroformate groups. The polymer solution was separated from thebrine and washed once with 1N HCl and four times with distilled water.The polymer solution was precipitated into boiling water (750 mL) in ablender, washed with water (500 mL) and dried overnight at 110° C. undervacuum. The polymer had a Tg of 143.7° C.

Example 7

A 1-liter glass melt polymerization reactor, which had been previouslypassivated by acid washing, rinsing and drying overnight at 70° C., wasloaded with 136.9 g (639 mmol) of diphenyl carbonate, 157.5 g (531 mmol)of BCC and 26.5 g (86 mmol) of SBI. A 316 stainless steel helicalstirrer was suspended in the powder and 151 microliters oftetramethylammonium hydroxide in the form of a 1.0 M aqueous solutionand 461 microliters of sodium hydroxide in the form of a 0.001 M aqueoussolution were added. The vessel was then evacuated and purged withnitrogen three times and heated to 180° C., whereupon the reactionmixture melted. Upon complete melting, it was allowed to thermallyequilibrate for 5-10 minutes and then the mixture was heated at 210° C.for 30 minutes with stirring. The pressure was then reduced to 240millibar, whereupon phenol began to distill from the reactor. After 45minutes, the pressure was reduced to 130 millibar and heating (at 240°C.) was continued for 45 minutes with continued distillation of phenol.Polymerization was continued further with the followingtemperature/pressure profile: 260° C./90 millibar (30 minutes); 260°C./20 millibar (15 minutes); 270° C./3 millibar (30 minutes); 270° C./1millibar (40 minutes); 300/1 millibar (90 minutes); 310° C./1 millibar(30 minutes). The polymer was then stranded from the reactor and cooledto give 170 g of slightly yellow strands (Mn=15100, Mw=35500, Tg=149°C.).

Example 8

Diphenyl carbonate (156.8 g, 732 mmol) DMBPC (120.5 g, 407 mmol), BPA(61.9 g , 271 mmol), 307 microliters of tetramethylammonium hydroxide inthe form of a 1.0 M aqueous solution and 460 microliters of sodiumhydroxide in the form of a 0.001 M aqueous solution were polymerized asin example 7 above. The polymer was then stranded from the reactor andcooled to give 172 g of nearly colorless strands (Mn=16600; Mw=37400,Tg=136° C.).

Comparative Example #1

BPA homopolycarbonate (LEXAN, optical quality grade, manufactured byinterfacial polymerization).

Comparative Example #2

BCC (11.8 g, 40 mmol), BPA (13.7 g, 60 mmol) and p-cumylphenol (1.06 g,5 mmol, 4.5 mol %) were reacted with phosgene as in Example 3 to affordafter isolation a polycarbonate having a glass transition temperature of140° C. The water absorption with 60 mol % BPA is 0.211%.

Comparative Example #3

A 500 mL Morton flask equipped as in Example 1 was charged with(4,4'-(m-phenylenediisopropylidene)diphenol (BPM) (19.0 g, 55 mmol),(1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (BPI) (13.9 g, 45mmol), p-tert-butylphenol (0.68 g, 4.5 mmol, 4.5 mol %), methylenechloride (125 mL), distilled water (90 mL) and triethylamine (200 uL).The reaction mixture was treated with 50 wt % NaOH to bring the pH to10.5. Phosgene (15.2 g) was added at 0.6 g/min maintaining the pH at10.5 by the addition of the NaOH solution. Residual phosgene was removedfrom the reaction mixture by sparging with nitrogen. The resultantpolymer solution was separated from the brine and washed once with 1NHCl and four times with distilled water. The polymer solution wasprecipitated into boiling water (750 mL) in a blender, washed with water(500 mL) and dried overnight at 125° C. under vacuum. The polymer had aMn of 13,300 Mw of 42,500 and a Tg of 138° C. ¹ H-NMR indicated thepresence of both BPM and BPI residues in a molar ratio of 55:45. Thewater absorption was 0.23%.

Table I summarizes the results of Examples 1-7 and comparative examples1,2 and 3

                                      TABLE I                                     __________________________________________________________________________         mole %                                                                            mole %                                                                            mole %                                                                            mole %           Cg   Cm                                       Exple BCC SBI CD-1 BPA % DDDA Mw Tg ° C. Brewster Brewster %                                                     H2O***                            __________________________________________________________________________    1    84  16  0   0   0    32,500                                                                            149 43   2000 0.16                                2 77 0 23 0 0 33,500 148 46 1900 0.153                                        3 100 0 0 0 0 35,200 138 47 2350 0.106                                        4 80 0 0 20 0 34,800 138 54.3 2910 0.127                                      5 60 0 0 40 0 33,300 139 59.7 3480 0.164                                      6 71 24 0  5 50,700 144 44.6                                                  7 84 16 0 0 0 35,500 149 38                                                   8 60 0 0 40 0 37,400 136 57.1                                                 comp 1 0 0 0 100 0 33,000 145 81 4400 0.35                                    comp 2 40 0 0 60 0  140 68.4 3940 0.211                                       comp 3*      42,500 138 44.5 2700 0.23                                      __________________________________________________________________________     *BPM:BPI = molar ratio of 55:45                                          

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:
 1. A polycarbonate comprising:(a) carbonate structural unitscorresponding to structure (I) ##STR16## where R₁ and R₂ areindependently selected from the group consisting of C₁ -C₆ alkyl;Xrepresents CH₂ ; m is an integer from 4 to 7; n is an integer from 1 to4; and p is an integer from 1 to 4 with the proviso that at least one ofR₁ or R₂ is in the 3 or 3' position; (b) carbonate structural unitsselected from the group consisting of(1) carbonate structural unitscorresponding to ##STR17## where R₃, R₄ and R₆ independently representC₁ -C₆ alkyl,each R₅ is independently selected from the group consistingof H and C₁ -C₃ alkyl and each n independently selected from the groupconsisting of 0,1 and 2, R₇ is H or C₁ -C₅ alkyl, (2) carbonatestructural units corresponding to ##STR18## where R₈, R₉, R₁₂ and R₁₃are independently C₁ -C₆ alkyl,R₁₀ and R₁₁ are independently H or C₁ -C₅alkyl, each R₁₄ is independently selected from the group consisting of Hand C₁ -C₃ alkyl and each n is independently selected from the groupconsisting of 0, 1 and 2; (3) carbonate structural units correspondingto ##STR19## where each R₁₅ is selected independently from the groupconsisting of H and C₁ -C₃ alkyl, and R₁₆ and R₁₇ are independently C₁-C₆ alkyl or aryl; (4) carbonate structural units corresponding tostructures (II) and (III); and (5) carbonate structural unitscorresponding to structures (III) and (IV), where the polycarbonate hasa glass transition temperature of from about 120° C. to about 185° C.and a water absorption of below about 0.33%.
 2. The polycarbonate asdefined in claim 1), wherein (a) is selected from the group consistingof residues of 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof. 3.The polycarbonate as defined in claim 2, wherein (b) is selected to becarbonate structural units of formula (III), the carbonate structuralunits of formula (III) further selected from the group consisting ofresidues of 6,6'-dihydroxy-3,3,3',3'-tetramethyl spirobiindane(SBI);6,6'-dihydroxy-3,3,5,3',3',5'-hexamethyl spirobiindane;6,6'-dihydroxy-3,3,5,7,3',3',5',7'-octamethylspirobiindane;5,5'-diethyl-6,6'-dihydroxy 3,3,3',3'-tetramethylspirobiindane andmixtures thereof.
 4. The polycarbonate as defined in claim 1), whereinboth R₁ and R₂ in structure (I) are in the 3 and 3' positions,respectively, and wherein n and p are both equal to
 1. 5. Thepolycarbonate as defined in claim 1, wherein component (a) is structuralunits of the formula: ##STR20## where R₁ and R₂ are CH₃.
 6. Thepolycarbonate as defined in claim 1, further comprising c) structuralunits corresponding to ##STR21## wherein Z is a C₁ -C₄₀ branched orunbranched alkyl or branched or unbranched cycloalkyl.
 7. Thepolycarbonate as defined in claim 1, wherein (a) comprises from 30 to 99mole % of the polycarbonate and (b) is selected to be carbonatestructural units of structure (II), the carbonate structural units ofstructure (II) comprising from 1 to 70 mole % of the polycarbonate. 8.The polycarbonate of claim 7, wherein the polycarbonate furthercomprises c) from 0.1 to 20 mole % of structural units of structure (V).9. The polycarbonate as defined in claim 1, wherein (a) comprises from30 to 99 mole % of the polycarbonate and (b) is selected to be carbonatestructural units of structure (III), the carbonate structural units ofstructure (III) comprising from 1 to 70 mole % of the polycarbonate. 10.The polycarbonate of claim 9, wherein the polycarbonate furthercomprises c) from 0.1 to 20 mole % of structural units of structure (V).11. The polycarbonate as defined in claim 1, wherein (a) comprises from30 to 99 mole % of the polycarbonate and (b) is selected to be carbonatestructural units of structure (IV), the carbonate structural units ofstructure (IV) comprising from 1 to 70 mol % of the polycarbonate, withthe proviso that when b) is exclusively BPA, b) comprises from 0.1 to 50mol % of the polycarbonate.
 12. The polycarbonate of claim 11, whereinthe polycarbonate further comprises c) from 0.1 to 20 mole % ofstructural units of structure (V).
 13. The polycarbonate as defined inclaim 1, wherein (a) comprises from 30 to 99 mole % of the polycarbonateand (b) is selected to be carbonate structural units of the structures(II) and (III), the carbonate structural units of the formulas (II) and(III) comprising from 1 to 70 mole % of the polycarbonate.
 14. Thepolycarbonate of claim 13, wherein the molar ratio of structural units(II) to structural units (III) is 1:99 to 99:1.
 15. The polycarbonate ofclaim 13, wherein the polycarbonate comprises from 0.1 to 20 mole % ofstructural units of structure (V).
 16. The polycarbonate as defined inclaim 1, wherein (a) is structural units of the formula: ##STR22## whereR₁ and R₂ are CH₃ ; and and (b) is structural units of the formula:##STR23##
 17. The polycarbonate of claim 16, wherein (a) comprises from30 to 99 mole % of the polycarbonate and (b) comprises from 1 to 70 mole% of the polycarbonate.
 18. The polycarbonate as defined in claim 1,wherein (a) is structural units of the formula: where R₁ and R₂ are CH₃and (b) is structural units of the formula: ##STR24##
 19. Thepolycarbonate of claim 18 wherein (a) comprises from 30 to 99 mole % ofthe polycarbonate and (b) comprises from 1 to 70 mole % of thepolycarbonate.
 20. The polycarbonate as defined in claim 1, wherein a)is structural units of the formula: wherein R₁ and R₂ are CH₃ ; and(b)is structural units of the formula: ##STR25##
 21. The polycarbonate ofclaim 20, wherein (a) comprises from 50 to 99 mole % of thepolycarbonate and (b) comprises from 1 to 50 mole % of thepolycarbonate.
 22. An article comprising the polycarbonate of claim 1.23. The article of claim 22, wherein the article is an optical article.24. The article of claim 22, wherein the article is an optical datastorage medium.
 25. The article of claim 19, wherein the article is asubstrate for optical data storage media.
 26. The article of claim 22,wherein the article is transparent.
 27. The article of claim 24, whereinthe optical data storage medium is a rewritable optical disk.
 28. Apolycarbonate comprising (a) carbonate structural units having thestructure ##STR26## where R₁ and R₂ are CH₃ ; and and (b) carbonatestructural units having the structure ##STR27## where the polycarbonatehas a glass transition temperature of from about 120° C. to about 185°C. and a water absorption of less than about 0.33%.
 29. Thepolycarbonate of claim 28, wherein the molar ratio of (a) to (b) is84:16.
 30. The polycarbonate of claim 28, wherein a) comprises comprisesfrom 30 to 99 mol % of the polycarbonate, and wherein b) comprises from1 to 70 mol % of the polycarbonate.
 31. An optical article comprisingthe polycarbonate of claim
 28. 32. An optical article comprising(A1)from 90 to 99.9999% by weight of a polycarbonate comprising(a) carbonatestructural units corresponding to structure (I): ##STR28## where R₁ andR₂ are independently selected from the group consisting of C₁ -C₆alkyl;X represents CH₂ ; m is an integer from 4 to 7; n is an integerfrom 1 to 4; and p is an integer from 1 to 4 with the proviso that atleast one of R₁ or R₂ is in the 3 or 3' position; (b) carbonatestructural units selected from the group consisting of(1) carbonatestructural units corresponding to structure (II): ##STR29## where R₃, R₄and R₆ independently represent C₁ -C₆ alkyl,each R₅ is independentlyselected from the group consisting of H and C₁ -C₃ alkyl and each nindependently selected from the group consisting of 0, 1 and 2, R₇ is Hor C₁ -C₅ alkyl, (2) carbonate structural units corresponding tostructure (III): ##STR30## where R₈, R₉, R₁₂ and R₁₃ are independentlyC₁ -C₆ alkyl,R₁₀ and R₁₁ are independently H or C₁ -C₅ alkyl, each R₁₄is independently selected from the group consisting of H and C₁ -C₃alkyl and each n is independently selected from the group consisting of0, 1 and 2; (3) carbonate structural units corresponding to structure(IV) ##STR31## where R₁₅ is selected independently from the groupconsisting of H and C₁ -C₃ alkyl, and R₁₆ and R₁₇ are independently C₁-C₆ alkyl or aryl; (4) carbonate structural units corresponding tostructures (II) and (III); and (5) carbonate structural unitscorresponding to structures (III) and (IV), where the polycarbonate hasa glass transition temperature of from about 120° C. to about 185° C.and a water absorption of below about 0.33%; and (A2) from 0.0001 to 10%of further additives.
 33. The optical article of claim 32, wherein thepolycarbonate further comprises structural units (V) ##STR32## wherein Zis a C₁ -C₄₀ branched or unbranched alkyl or branched or unbranchedcycloalkyl.
 34. The optical article of claim 32, wherein (a) isstructural units of the formula: ##STR33## where R₁ and R₂ are CH₃ ; and(b) is structural units of the formula: ##STR34##
 35. The opticalarticle of claim 32, wherein the optical article is a medium for opticaldata storage.
 36. The optical article of claim 32, wherein the opticalarticle is a substrate for optical data storage media.
 37. The opticalarticle of claim 32, wherein the optical article is a compact disk foraudio data storage.
 38. The optical article of claim 32, wherein theoptical article is a rewritable optical disk.
 39. The optical article ofclaim 32, wherein the optical article is a WORM optical disk.
 40. Amethod of making an optical article comprising the step of molding amolding composition comprising a polycarbonate, the polycarbonatecomprising: (a) carbonate structural units corresponding to structure(I) ##STR35## where R₁ and R₂ are independently selected from the groupconsisting of C₁ -C₆ alkyl;X represents CH₂ ; m is an integer from 4 to7; n is an integer from 1 to 4; and p is an integer from 1 to 4 with theproviso that at least one of R₁ or R₂ is in the 3 or 3' position; and(b) carbonate structural units selected from the group consisting of(1)carbonate structural units corresponding to ##STR36## where R₃, R₄ andR₆ independently represent C ₁ -C₆ alkyl,each R₅ is independentlyselected from the group consisting of H and C₁ -C₃ alkyl and each nindependently selected from the group consisting of 0, 1 and 2, R₇ is Hor C₁ -C₅ alkyl, (2) carbonate structural units corresponding to##STR37## where R₈, R₉, R₁₂ and R₁₃ are independently C₁ -C₆ alkyl,R₁₀and R₁₁ are independently H or C₁ -C₅ alkyl, each R₁₄ is independentlyselected from the group consisting of H and C₁ -C₃ alkyl and each n isindependently selected from the group consisting of 0, 1 and 2; (3)carbonate structural units corresponding to ##STR38## where R₁₅ isselected independently from the group consisting of H and C₁ -C₃ alkyl,and R₁₆ and R₁₇ are independently C₁ -C₆ alkyl or aryl; (4) carbonatestructural units corresponding to structures (II) and (III); and (5)carbonate structural units corresponding to structures (III) and (IV),where the polycarbonate has a glass transition temperature of from about120° C. to about 185° C. and a water absorption of below about 0.33%.41. The method of claim 40, wherein the optical article is a medium foroptical data storage.
 42. The method of claim 40, wherein the opticalarticle is a substrate for optical data storage media.
 43. Apolycarbonate consisting essentially of 84 mol % BCC and 16 mol % SBI,where the polycarbonate has a glass transition temperature of belowabout 150° C. and a water absorption of below about 0.2%, and a C_(g)below about 50 Brewsters and a Cm of less than about 2500 Brewsters. 44.An optical article comprising the polycarbonate of claim
 43. 45. Amethod of making a polycarbonate comprising 84 mol % BCC and 16 mol %SBI, the method comprisingA) mixing BCC monomer and SBI monomer in amolar ratio of BCC:SBI of 84:16 with a carbonate source in the presenceof a catalyst, thereby forming a reaction mixture; B) heating thereaction mixture until the reaction mixture melts; C) thermallyequilibrating the mixture; and D) increasing the molecular weight byremoving volatile components from the reaction mixture in one or morereaction stages.
 46. A polycarbonate prepared according to the method ofclaim
 45. 47. A polycarbonate comprisinga) structural units selectedfrom the group consisting of residues of1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;1,1-bis(4-hydroxy-3-methylphenyl)cyclopentane;1,1-bis(4-hydroxy-3-methylphenyl)cycloheptane and mixtures thereof; andb) structural units selected from the group consisting of residues of6,6'-dihydroxy-3,3,3',3'-tetramethyl spirobiindane(SBI);6,6'-dihydroxy-3,3,5,3',3',5'-hexamethyl spirobiindane;6,6'-dihydroxy-3,3,5,7,3',3',5',7'-octamethylspirobiindane;5,5'-diethyl-6,6'-dihydroxy 3,3,3',3'-tetramethylspirobiindane andmixtures thereof, where the polycarbonate has a glass transitiontemperature of from about 120° C. to about 185° C. and a waterabsorption of below about 0.33%.
 48. An optical article comprising thepolycarbonate of claim
 47. 49. A medium for optical data storagecomprising the polycarbonate of claim
 47. 50. A substrate for opticaldata storage media comprising the polycarbonate of claim
 47. 51. Apolycarbonate comprising from about 80 to about 85 mol % of structuralunits derived from BCC and from about 15 to about 20 mol % of structuralunits derived from BPA.
 52. A medium for optical data storage comprisingthe polycarbonate of claim
 51. 53. A substrate for optical data storagemedia comprising the polycarbonate of claim 51.